Compounds represented by the general formula (II): ##STR1## (where R.sub.1 is a lower alkyl group and R.sub.2 is a lower alkyl group) are described in Japanese Patent Public Disclosure No. 56873/1994, etc. and are known to have a capability for promoting the movement of digestive tracts.
Process for producing these compounds are described in Japanese Patent Public Disclosure No. 56873/1994, Bioorg. & Med. Chem. Lett., Vol. 4, No. 11, p. 1347, 1994, etc.
However, the processes described in these references have several drawbacks that make them unsuitable for commercial operations, such as the multitude of the steps involved, much use of column chromatography for purification and the use of reagents (e.g., iodine) that are unsuitable for large-scale production. Further, the compounds are required to have high quality in such terms as stability, uniformity and compliance with standards if they are to be used for supplying pharmaceuticals or starting materials therefor of the kind that is to be produced by the process of the invention.